面试题10之二进制中1的个数_NumberOf1InBinary.cpp

// NumberOf1InBinary.cpp : Defines the entry point for the console application.
//

// 《剑指Offer——名企面试官精讲典型编程题》代码
// 著作权所有者：何海涛

#include "stdafx.h"

int NumberOf1_Solution1(int n)
{
    int count = 0;
    unsigned int flag = 1;
    while(flag)
    {
        if(n & flag)
            count ++;

        flag = flag << 1;
    }

    return count;
}

int NumberOf1_Solution2(int n)
{
    int count = 0;

    while (n)
    {
        ++ count;
        n = (n - 1) & n;
    }

    return count;
}

void Test(int number, unsigned int expected)
{
    int actual = NumberOf1_Solution1(number);
    if(actual == expected)
        printf("Solution1: Test for %p passed.\n", number);
    else
        printf("Solution1: Test for %p failed.\n", number);

    actual = NumberOf1_Solution2(number);
    if(actual == expected)
        printf("Solution2: Test for %p passed.\n", number);
    else
        printf("Solution2: Test for %p failed.\n", number);

    printf("\n");
}

int _tmain(int argc, _TCHAR* argv[])
{
    // 输入0，期待的输出是0
    Test(0, 0);

    // 输入1，期待的输出是1
    Test(1, 1);

    // 输入10，期待的输出是2
    Test(10, 2);

    // 输入0x7FFFFFFF，期待的输出是31
    Test(0x7FFFFFFF, 31);

    // 输入0xFFFFFFFF（负数），期待的输出是32
    Test(0xFFFFFFFF, 32);

    // 输入0x80000000（负数），期待的输出是1
    Test(0x80000000, 1);

    return 0;
}